Photoluminescence Properties, Judd-Ofelt Analysis, and Energy Transfer Mechanisms in Ca3ga4o9:Dy3+ Phosphor: High Thermal Stability and White-Light Emitting Diode Potential

Abstract

In this study, we present the synthesis of a series of single-phase Dy3+-activated Ca3Ga4O9 phosphors using a high-temperature solid-state method for applications in white light-emitting diodes (wLEDs). The phase purity and crystal structure of the synthesized phosphors were verified by examining their X-ray powder diffraction patterns. To investigate the influence of doping on the band gap, we recorded diffuse reflectance spectra. Additionally, surface morphology and elemental composition were analyzed using field emission scanning electron microscopy and energy-dispersive X-ray spectroscopy. In order to understand the impact of doping on structural properties and the distribution of different charges and elemental oxidation states, time-of-flight secondary ion mass spectroscopy and x-ray photoelectron spectroscopy were employed. Photoluminescence excitation and emission studies revealed energy transfer from the host to the activator, which was further confirmed by Cathodoluminescence emission spectra and decay behavior. Dipole-dipole interactions were identified as the underlying mechanism for energy transfer and concentration quenching phenomena among activator ions. Judd-Ofelt (JO) analysis demonstrated a higher sensitivity of the JO intensity parameter Ω2 to the ligand environment. Thermal studies indicated the excellent thermal stability of the synthesized phosphors up to 673.15 K, with an activation energy of 0.28 eV. Furthermore, chromaticity analysis revealed that the International Commission on Illumination coordinates for 1 mol% (0.3259, 0.3475) were in close proximity to the standard white point (0.3333, 0.3333), resulting in a correlated color temperature of 5798 K. This comprehensive analysis strongly supports the potential of the synthesized phosphor as an efficient candidate for near ultra-violet-activated wLEDs.

Keywords: Phosphor, Time-of-Flight Secondary Ion Mass Spectroscopy, X-ray Photoelectron Spectroscopy, Judd-Ofelt, Energy-transfer, White emission